Geodetic devices typically have a base forming a first device component that may for instance be mounted onto a tripod. The first device component supports a second device component being rotatable relative to the first device component about a first axis of rotation. The base is usually oriented, for example by adjusting the tripod, such that the first axis of rotation is aligned vertically in space, i.e. parallel to the direction of gravitation. The second device component supports a third device component comprising for instance optics having a measurement axis and being rotatable relative to the second device component about a second axis of rotation. This measurement axis may form a line of sight of the geodetic device along which measurements using the optics can be performed, like for instance angular measurements or distance measurements. The first and the second axis of rotation are basically aligned orthogonally with each other. A first angle sensor is provided to determine a rotational position of the second device component with respect to the first device component, and a second angle sensor is provided to determine a rotational position of the third device component with respect to the second device component. In order to associate a measurement performed for instance with the optics along the measurement axis with a spatial direction, the alignment of the measurement axis of the third device component can be determined with respect to the base of the device from the measurement values obtained from the first angle sensor and the second angle sensor.
Since a user will, when adjusting e.g. the tripod for the first device component manually, only be able to approximately align the first axis of rotation in parallel with the gravitational direction, a high-precision inclination sensor is usually mounted on the first device component or the second device component for enabling a precise determination of the alignment of the first axis of rotation with respect to the gravitational direction. A measurement value obtained from the inclination sensor is then included in the calculation of the alignment of the optics' measurement axis based on the measurement values obtained from the first and second angle sensors.
The measurement range of high precision inclination sensors is, however, limited to, for example, less than 1°. This limited measurement range forms a portion of the possible orientations of the inclination sensor in which the sensor is enabled to determine its orientation relative to the gravitational direction with a specified preciseness. A user is then required to align the base and thus the inclination sensor with such a precision that the inclination sensor is disposed within its measurement range. This is time-consuming and limits the possible alignments of the base of the geodetic device. Further, even the measurement signals output from high-precision inclination sensors are possibly not exactly proportional to the actual alignment of the inclination sensor with respect to the gravitational direction and therefore error-prone.
In addition, it is assumed, when determining the spatial alignment of the measurement axis like the optics' measurement axis based on the measurement values obtained from the first and second angle sensors as well as from the inclination sensor, that the angle between the first axis of rotation and the second axis of rotation is exactly 90°. Due to the device's assembling tolerances and due to deformations caused by the proper weight of the device components this is in practice only approximately true.
It is therefore an object of the present invention, to provide a device and a method for operating the device, the device enabling a determination of device parameters comprising in particular at least one of the alignment of the first device component with respect to the gravitational direction, the alignment of the first axis of rotation with respect to the second axis of rotation, and a characteristic of the inclination sensor.